Iran’s petrochemical exports have plunged nearly 90 percent in the last two weeks, according to traders and shipping data.

That is because most shipping firms cannot get insurance to transport cargoes due to EU sanctions.

The sanctions banning European insurers and reinsurers from covering tankers carrying Iranian petrochemicals came into effect at the start of May.

Similar EU measures aimed at crude and oil products will start in July.

“Petrochemicals are definitely an indication of what could happen to crude, but I doubt the impact will be as strong,” said Erik Nikolai Stavseth, a shipping analyst with Arctic Securities.

Shipping data confirmed a sharp drop in Iranian petrochemical exports, which includes methanol, xylene and caustic soda, to around 60,000 tonnes a week in May from a weekly average of 350,000 tonnes last year.

OPEC’s second-largest oil producer could be exporting more petrochemicals than what is evident from shipping data, as captains on some of Iran’s ships have turned off the black box transponders that monitor vessel movements.